Not able to preseed snaps from private snap store

[Aristo Chen]

[Summary]
I was using ubuntu-image(Version: 3.2, revision: 702) snap to build a classic image for customer, and the gadget snap is in the customer's private store, and looks like the ubuntu-image is not able to download snaps from private store

[Steps]
1. Prepare model.assert that contains gadget snap from private store
2. Prepare a credential that is allowed to access the private store
3. Use the command
   $ sudo 'UBUNTU_STORE_AUTH_DATA_FILENAME=$(pwd)/store.auth' /snap/bin/ubuntu-image classic --debug -O out -w work yaml/server-arm64.yaml --disk-info buildstamp

[Result]
```
[8] clean_extra_ppas
duration: 2.651111ms
[9] install_extra_snaps
Fetching nvent-9400i-mod-0001-gadget-classic (5)
duration: 6.455209737s
Error: Error preparing image: received an unexpected http response code (404) when trying to download https://api.snapcraft.io/api/v1/snaps/download/zp3fpAbvfNg8DT0o5PZTcjZiwRzAeI1d_5.snap
```

[Other Info]
Previously with ubuntu-image 2.x, we can set UBUNTU_STORE_AUTH_DATA_FILENAME=store.auth as env variable for ubuntu-image to consume, then it will have the permission to download snaps from private store, but looks like ubuntu-image 3.x does not support this mechanism

[Paul Mars (upils)]

Hey Aristo,

Ubuntu-image is preparing the snaps by using the snapd lib. From what I can see in the code, the env var UBUNTU_STORE_AUTH_DATA_FILENAME is still used in snapd, so this should still work.

We do not have test on this feature so I cannot confirm there is a bug without testing with a private store.

Are you sure the account you used is authorized to access the private store? Are you sure the macaroon in the store.auth file did not expire?

[Aristo Chen (aristochen)]

Hi @Paul

Yes, I am sure the credential is not expired.

In the same script that I was using for building the image, I need to use the credential to download the same gadget snap from the private store, and it succeed, so I assume ubuntu-image 3.x should be able to use the same credential without issue.

[Aristo Chen (aristochen)]

Hi,

it turns out that our build script is not handling the variables properly, so it is not a bug in ubuntu-image, sorry for bothering, and I will switch the bug status to invalid.